黄土高原北部典型灌丛枝条生物量估算模型

Stem biomass estimation models for dominant shrubs on the northern Loess Plateau of China

于2015年8月末在陕西神木县六道沟小流域采集200个柠条和210个沙柳枝条,测定枝条的基径(D)、长度(H)、含水量(W_0)、鲜质量(W_F)和干质量(W),选用指数函数和异速生长方程建立了4种由枝条形态指标估算枝条生物量的简易模型,并对模型的拟合效果进行验证.结果表明:对于柠条和沙柳灌丛,基于D、H二者组合变量(D^2H)的异速生长方程是估算枝条生物量的最优模型,该模型经线性转化后可以消除生物量数据的异方差性,且拟合效果最优,决定系数(R^2)最大,平均误差(ME)、平均绝对误差(MAE)、总相对误差(TRE)、平均系统误差(MSE)和平均绝对百分误差(MPSE)整体上最小,基本满足生态学研究的精度要求.

A total of 200 stems of Caragana korshinskii and 210 stems of Salix psammophila were collected in the late August of 2015 in the Liudaogou catchment of Shenmu County,Shaanxi Province,China.Basal diameter（D）,length（H）,water content（W0）,fresh mass（WF） and dry mass（W） were measured for each stem of the two species.Exponential and allometric equations were used to establish relationship models relating stem biomass to its morphological parameters.Altogether four models were established for each species,and their accuracy of estimation was also validated.The results showed that,the allometric model that used D2H as input variable was optimal in estimating stem biomass for C.korshinskii and S.psammophila,after transformed into its linear form.Meanwhile,the heteroscedasticity of the biomass data was greatly eliminated.This model had a maximum value of coefficient of determination（R2）,and meanwhile minimum values of mean error（ME）,mean absolute error（MAE）,total relative error（TRE）,mean systematic error（MSE）,and mean absolute percentage error（MPSE）,thus basically meeting the requirement of the accuracy in ecological study.